The city of Dayton is demanding the Air Force act more urgently to prevent the potential of groundwater contamination from the base to the city’s Huffman Dam well field along the Mad River. In this photo, ice flows down the Great Miami River, right at the confluence with the Mad River at Deeds Point. TY GREENLEES/STAFF

Here are five things to know about the issue:

CITY WELLS SHUT DOWN: The city shut down seven groundwater drinking wells at Huffman Dam along the Mad River last April out of concerns groundwater contamination from Wright-Patterson could seep into the wells.

BASE WELLS SHUT DOWN: Separately, the Ohio EPA ordered Wright-Patterson to shut down two groundwater wells on the base in 2016. Those wells were restarted last year when the base installed a $2.7 million facility to treat the groundwater. Base officials say the treated water is safe to drink.

WATER SAFETY: State and city leaders say the city’s water is safe and no contamination from the firefighting foam has been provided to customers. For the first time, Dayton detected polyfluoroalkyl substances in raw water intake late last year at its Ottawa treatment facility, but the contamination of less than 10 parts per trillion was below an EPA threshold of 70 parts per trillion for lifetime exposure. The contaminant has been linked to an old formula for aqueous film forming foam firefighters sprayed to extinguish fuel-fed fires and to conduct training.

COSTS ADDING UP: The city of Dayton has asked the Air Force to reimburse it for costs nearing $1 million for expenses associated with the Huffman Dam well field shutdown and ongoing environmental testing and studies.

EPA CITES WRIGHT-PATTERSON: In January, the Ohio EPA cited Wright-Patterson over frustrations the Air Force was not acting quickly enough to prevent the potential spread of the contaminated groundwater towards the city well field. It has given the city a month to come up with a comprehensive work plan to address the issue.